This invention relates to the transfer of data between two points and, in particular, to a Universal Transfer Mode of transferring data from a plurality of sources that may operate under different communications protocols to a plurality of sinks using switch modules interconnected by a passive core.
Modern telecommunications services are supported by a plurality of networks. The various networks operate under protocols that use packets of various lengths and formats to transfer data between a source and a sink. Modern telecommunications services provide the capability for business and social communications between geographically separated parties. This capability has stimulated a demand for such services and placed a burden on the capacity of existing infrastructure.
In order to increase the capacity for information exchange using the existing infrastructure, there has developed an interest in using asynchronous network facilities such as Asynchronous Transfer Mode (ATM) networks as backbone transport for voice and voice data as well as broadband services. Asynchronous network facilities are preferred for backbone transport because they permit more efficient use of network resources than synchronous transfer mode (STM) facilities. Network cost is therefore reduced. The ATM protocol uses a fixed cell length of 53 bytes. Consequently, packets originating in a network that operates under a different protocol must be deconstructed and packed in ATM cells before they can be transferred through the ATM network. After the packets are transferred through the ATM network, they must be unpacked from the cells and reconstructed before the cells are delivered to a sink. This is a time consuming task that can impact service delivery and quality of service.
Some telecommunications protocols such as Internet Protocol (IP) support packets of variable length. IP is unsuitable for certain telecommunications services, however, because it is connectionless and offers no guaranteed quality of service. Recent work has been done to develop protocols for providing quality of service in IP networks. Resource Reservation Protocol (RSVP) is, for example, one result of such work. Even if quality of service is successfully implemented in IP networks, however, packet addressing and routing in such networks is too processing intensive to permit a high-speed multi-service scalable network to be implemented.
As the demand for telecommunications services increases, service providers seek cost effective methods of service delivery. One way to provide cost effective service delivery is to provide a backbone transport network that is capable of supporting a variety of narrow-band and broadband services so that network provisioning and management costs are shared by a large and diverse user base. Ideally, such a backbone transport network is adapted to support many different telecommunications services and both connection-based and connectionless protocols. To date, no such network is known to have been proposed or described.
It is therefore an object of the invention to provide a Universal Transfer Mode (UTM) protocol for transferring telecommunications data in packets from a plurality of sources which may operate under different protocols to a plurality of sinks.
It is a further object of the invention to provide a network specifically adapted to operate under the UTM protocol.
It is yet a further object of the invention to provide a protocol and a network which are adapted to transfer packets of substantially any length without packet fragmentation.
It is yet a further object of the invention to provide a protocol and a network which are adapted to transfer both connectionless and connection-based data traffic.
It is another object of the invention to provide a protocol and a network which are adapted to enable rate regulated data packet transfer in a multi-class data network.
It is yet a further object of the invention to provide a protocol that uses an adaptive header for both control signaling and for payload transfer.
It is yet a further object of the invention to provide a UTM protocol in which the adaptive header is used as a control packet for setting up or tearing down a path, a connection within a path or an independent connection with the UTM network.
It is yet a further object of the invention to provide a UTM protocol in which the adaptive header is parsed by a simple algorithm to determine a function of the header and a destination for packets appended to the header.
It is yet another object of the invention to support the optional subdivision of data in a connection-based data packet into sub-fields to support multi-type communications.
In its simplest aspect, a protocol for data transfer in a data network that transfers variable length payload data packets comprising:
an adaptive header that is parsed to interpret a purpose and a destination for each packet transferred within the data network, the payload packets being appended to the adaptive header to effect the transfer of the payload packets through the data network, and the adaptive header being used alone as a control packet for control messages exchanged in the data network.
The invention further provides a UTM distributed switch, comprising a plurality of modules, each module interfacing with a plurality of links, the modules accepting data to be routed through universal ports which transfer packets of variable size to others of the plurality of modules; a passive core that logically interconnects each of the modules to each of the other modules and transfers the data between the modules under control of the modules; the traffic between any source and a sink being rate regulated.
The invention also provides a method of transferring telecommunications data in packets from a plurality of sources to a plurality of sinks comprising the steps of accepting a communications admission request from a source at an interface at a module port that operates under a universal transfer mode (UTM) protocol, the communications admission request providing communications admission control parameters required for establishing a communications session between the source and a sink; for a connection-oriented transaction, setting up a connection for the communications session through the UTM network; accepting the packets from the source at the interface and determining a length of each packet; and transferring the packet to an interface that serves the sink using the connection or destination identifier.
The UTM protocol and the UTM network in accordance with the invention provide rate regulated data transfer between a source and a sink. Both connectionless and connection-based traffic may be served. The UTM protocol accommodates a plurality of classes of service, which ensure a quality of service appropriate to the data being transferred. Transfer through the UTM network is accomplished using an adaptive UTM header that is parsed by UTM modules using a simple algorithm that is preferably implemented in hardware. The algorithm determines a purpose and a destination of each packet transferred through the UTM network.
The adaptive UTM header is also used for control signaling in the UTM network. When used for control signaling, the adaptive header of a UTM control packet is transferred through the network as required to set up or take down a path, a connection within a path or an independent connection. Independent connections are preferably used in the UTM network only for high bit rate connections. For low bit rate connections, the preferred method of transfer is a connection within a path. Once a path is established between two modules in the UTM network, it can support as many connections as the capacity of the path permits. In setting up a connection within a path, only the originating module needs to deal with resource allocation and resource usage tracking. This significantly improves the connection setup rate in the UTM network.
The UTM network preferably comprises a plurality of edge modules switch that are interconnected by a passive core. The core is preferably optical and includes optical cross-connects. In the preferred embodiment, the passive core provides a high connectivity. Preferably, not more than two hops are required to establish a connection between any two modules. The edge modules include universal ports connected to the optical core and ingress/egress ports connected to various service networks. Ingress ports accept data packets from a source and append them to an adaptive header. The adaptive header indicates a destination for the packet, which is used to route the packet across the module, and through the passive core. At a destination module, the adaptive header is removed from the packet and the packet is transferred to a sink in its native format. Thus, packets of any supported format may be transferred through the UTM network without fragmentation. Consequently, the complications associated with the deconstruction and reconstruction of packets are avoided.
Traffic in the UTM network is rate regulated from end to end. Rate regulation is accomplished using a control element associated with each module and a packet scheduler associated with each egress link controller in each module. The control element handles traffic admission requests and assigns a rate allocation to each connection. The packet scheduler handles packet transfer in accordance with the rate allocations. Packet scheduling is facilitated by sorting payload packets by destination and by class of service. Parallel adders are used in the packet scheduler to ensure that packets are transferred at link speed so that the full capacity of the UTM network is available for packet transfer.
Connectionless traffic is served by inserting a destination in the adaptive header appended to a connectionless packet. When the network is busy, connectionless traffic uses free time intervals. If the full capacity of the network is not being used, the connectionless traffic is preferably allocated a connection and assigned a connection number that permits the connectionless packets to be transferred more efficiently through the network. When the connection allocated to the connectionless traffic is required by connection-based traffic, the connection allocated to the connectionless traffic is revoked, or its allocated bit rate is reduced, and the connectionless traffic reverts to being forwarded in unoccupied packet time intervals.
Another important feature of the UTM protocol is the optional subdivision of the data field of a connection-based data packet into sub-fields to support multi-type communications commonly referred to as xe2x80x9cmulti-mediaxe2x80x9d communications. For example, a keen interest exists in the capacity to transmit sound and video simultaneously in a data packet to support live video. Some applications may also require the transfer of text with live video. For example, educational lectures commonly consist of voice, video and text presentations. The adaptive header in accordance with the invention supports the transfer of packets that include predefined sub-fields to support such services.